Why does Harold choose to lock down the machine again?

Question

In Person Of Interest, Harold designs an AI that can predict crime and terrorism. He "locks down" the machine because he cannot foresee the consequences of its growing intelligence and because he wants to prevent any human from exploiting it for malicious ends.

But, in series 5, the machine is reassembled after being attacked by Samaritan (the evil AI) but it is reassembled as an open system and it performs well to protect Harold and his friends.

In S5E10 Harold choses to close the system again.

Why does he do this when it has been so useful to have an open system?

Answer 1

The machine is kept as a closed system to be save from being abused by people. In Season 5, it is being used by Finch and his team, so they are using it for the pure good of saving lifes.

But if Finch left it open, what will happen, in future, when it comes into the hands of other people? Like, in the end, Finch is not involved but Shaw and Fusco are primary assets. Also, the machine is recruiting new people, so one of them may plan to use the knowledge.

Even good people can end up misusing it if given that much power. In fact, Samiritian is not pure evil, it also wants the good of overall humanity. So, retraining the AI is a must.

Also, keeping the system closed makes it easier to be save from hacking. Hackers are very common and strong in the PoI universe. Even the goverment hired people to look into the machine and they exploit even a single backdoor. Making an open system means unlimited power to be explioted.